When planting with a conventional row-crop planter such as a John Deere MaxEmerge® or MaxEmerge® Plus planter, it is recognized that sufficient down force must be exerted on the row unit to ensure full penetration of the furrow opening disk blades into the soil to the pre-selected furrow depth and also to provide some degree of soil compaction by the gauge wheels to ensure proper furrow formation. It is also recognized, however, that excessive down force will cause over compaction of the soil which may, in turn, result in improper root growth and/or poor germination due to re-opening of the furrow.
FIGS. 1, 4 and 7 are intended to represent soil profiles under the furrow opening assembly 34 of a conventional planter that is subject to differing amounts of down force. Specifically, FIG. 1 illustrates a soil profile with an ideal amount of down force being exerted so as to achieve full penetration to the preset depth of the disk blades 44, 46 and with just enough compaction exerted on the surrounding soil by the gauge wheels 48, 50 to ensure proper furrow formation but without excess soil compaction of the surrounding soil. FIG. 2 represents the same soil profile after the seed 42 is deposited but prior to being covered with soil by the furrow closing assembly 36. FIG. 3 is intended to represent that same soil profile after being covered with soil by the furrow closing assembly 36.
FIGS. 4-6 are similar to FIGS. 1-3 but are intended to represent the effects of too little down force being exerted by the gauge wheels 48, 50. In such a situation, the disk blades 44, 46 may not penetrate into the soil to the full desired depth and/or the soil may collapse into the furrow 38 as the seeds 42 are being deposited resulting in irregular seed depth.
FIGS. 7-9 are also similar to FIGS. 1-3 but represent the effects of excessive down force being applied. The soil is being compacted excessively adjacent to the seed furrow 38 resulting in substantial differences in soil density between the furrow walls when compared to the soil density on either side of the furrow. Under such extreme conditions, the compaction of the furrow walls and the soil below the furrow 38 prevents the roots from easily penetrating the adjacent soil, which may result in the roots being prevented from growing conically downward perpendicular to the direction of the furrow. Poor root penetration may result in weak stands and may place the crops under unnecessary stress during drier conditions. In addition to inadequate root penetration, as illustrated in FIG. 9, when the soil is overly compacted by the gauge wheels, the furrow may re-open along the centerline of the furrow due to the differing soil densities as the soil dries out, resulting in poor seed-to-soil contact and/or drying out of the seed causing poor germination and seedling death.
Heretofore, growers could only speculate as to whether the amount of downforce set for the planter was appropriate by observing the soil profile after planting a stretch of soil to determine the looseness or compactness of the soil around the seed furrow. Simply visually inspecting the soil is imprecise and it is difficult for most growers to accurately judge whether or not they are planting with too little or too great of downforce. Furthermore, the appropriate amount of downforce to be applied may be different across the field due to varying soil conditions.
U.S. Pat. No. 6,389,999 to Duello (hereinafter “Duello '999) describes a system for dynamically controlling excess downforce during planting operations by employing a pressure sensor, such as a strain gauge or other pressure transducer, placed on or incorporated into the gauge wheel mounting structure to detect the compressive forces being exerted upon the gauge wheel mounting structure. Duello '999 further describes the use of a microprocessor, or the like, adapted to receive the signals from the pressure sensor and to actuate the planter's hydraulic system or a supplemental down-pressure system to regulate the amount of down force exerted on the planter row units in relation to a value previously selected by the grower. Duello '999 further discloses that the pre-selected down force value may be variable based on pre-selected values entered into field mapping system utilizing global positioning.
U.S. Pat. No. 6,701,857 to Jensen et al. (hereinafter “Jensen '857”) also discloses a system for automatically adjusting the downforce during planting operations. Specifically, Jensen '857 discloses the use of a Wheatstone bridge strain gage circuit applied to the gauge wheel arms to detect the amount of strain due to bending stresses exerted on the arms. The strain exerted on the gauge wheel arms corresponds to the change in resistance or output voltage of the Wheatstone bridge circuit. The output voltage is transmitted to a closed loop electronic control unit connected to the electrical and hydraulic or pneumatic system of the tractor used for regulating the downforce applied by the planter. A micro-processor functions to compare the detected downforce to a downforce value pre-selected by the grower and to automatically actuate the planter's hydraulic or pneumatic system accordingly to increase or decrease the downforce as required to maintain the detected downforce at or near the pre-selected downforce value. Jensen also proposes the concept of measuring a shear load at a pin in the depth control mechanism but fails to provide any discussion or drawing figures on how to do so.
While the foregoing patents describe the benefit of being able to monitor and control downforce during planting operations and the general theory of utilizing a pressure sensor in the “gauge wheel mounting structure” (Duello '999) or on the “gauge wheel arms” (Jensen '857) neither patent describes in sufficient detail a practical working embodiment that can accurately and consistently determine and monitor down force during planting operations. For example, changes in the depth setting of the planter unit can result in a different loading conditions on the gauge wheel arms and gauge wheel mounting structure which can vary the output signal of the pressure sensor. Additionally, due to the location, the sensitive gauges and wires used for monitoring the downforce must be shielded or protected to avoid damage from debris during planting operations.
Accordingly, there remains a need for a system for monitoring downforce on a planter row unit that is robust yet economical to produce and that provides accurate measurements (preferably without calibration) regardless of the position of the depth regulation member.